Study Of Denitrifying Sulfide Removal Process And Enhancement Of Elemental Sulfur Reclamation Under Micro-aerobic Conditon From Wastewater Of High Carbon To Nitrogen Ratio

Treatment of wastewater containing high concentration of nitrate and sulfate orsulfide by denitrifying sulfide removal （DSR） process proved to be successful.Although a lot of researches on DSR were carried out at low concentration of organiccarbon compounds, the process was not deeply studied concerning its application foreffluents containing high organic carbon concentrations. Current DSR processcontaining high concentration of organic carbon can’t reach high sulfur productivity.This study discussed hydraulic retention time （HRT） control strategy influencing theprocess operation in order to enhance the performance of DSR process and increasethe elemental sulfur （S0） reclamation under anaerobic condition. Enhancedperformance of denitrifying sulfide removal under micro-aerobic condition with highorganic carbon to nitrogen ratio was also conducted to maximize the elemental sulfurreclamation.This study evaluated two kinds of control strategy on elementary sulfurbiotransformation in DSR process, at a carbon to nitrate （C/N） ratio of3. The effectof HRT on DSR process was investigated in a continuous expanded granular sludgebed （EGSB） bioreactor with C/N=3and S/N=5:6. At HRT of30h a maxim ofelemental transformation efficiency of0.53kg·m^-3·d^-1was obtained with a sulfideremoval rate of83.2%. Decreasing the S/N to5:8achieved higher elemental sulfurreclamation but a lower sulfide removal rate.The effect of dissolved oxygen （DO） on DSR process was investigated using acontinuous EGSB bioreactor at loading rate of1.6kgS2-·m^-3·d^-1,2.1kgAC--C·m^-3·d^-1,0.8kgNO-33-N/·m-·d^-1with HRT of12h. Results of continuous EGSBreactor under DO concentration of0.1±0.01mg/L and0.15±0.01mg/L showed a hugeenhancement of DSR process compared to anaerobic conditions. Sulfide removal ratewas increased from51.7%to71.4%and85.0%respectively; elemental sulfurreclamation rose from32.2%to61.4%and81.8%. Effluent elemental sulfur loadingrate were raised from0.48kgS0·m^-3·d^-1to0.76kgS0·m^-3·d^-1and1.00kgS0·m^-3·d^-1,.Startup of DSR under micro-aerobic condition proved a good way to reach arelatively high elemental sulfur conversion.